When to use computer-based power analysis tools

Manuel E. Hernandez, PE, Primera Engineers Ltd., Chicago

12/05/2013

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Software packages

The key to knowing when to invest in these programs is to really understand what the company’s typical project portfolio is. If a company is traditionally hired to do electrical design on large projects that consist of multiple bus points and equipment, then a power analysis software package can be a useful tool. With the creation of the Microsoft Windows operating system, electrical system analysis programs have evolved drastically. Programmers, as stated before, have been working to meet the needs of their users with every update. SKM Systems Analysis, ETAP, EasyPower, and CYME Power Engineering Software are good examples of how programmers took advantage of the Windows operating system.

SKM is the one of the most widely used software packages in the industry. SKM has been around since the 1970s when its calculation modules used a basic spreadsheet format. It wasn’t until Windows 95 was introduced that SKM released Power Tools for Windows (PTW), and the rest is history. With PTW, SKM managed to combine all of its modules into the same platform, making it extremely convenient to have everything in one package. PTW carries a long list of calculation modules, but DAPPER is its primary product. DAPPER, or Distribution Analysis for Power Planning Evaluation and Reporting, performs all basic calculations needed for a project and more. This module performs demand load analysis, load flow voltage drop, motor starting simulation, traditional fault analysis, and load schedule documentation. It also performs feeder, raceway, and transformer sizing, but engineers should always maintain control of this task. It helps them catalog the decisions they made so they have a record when clients or reviewers make inquiries regarding sizing equipment.

ETAP is another widely used software package that can simulate power systems. Its history can be traced back to early 1990s when, in collaboration with Texaco, it became one of the powerhouses in power management with its real-time monitoring, helping customers in controlling operation, maintenance, and planning of their electrical power system. Throughout the years, ETAP has consistently added modules to its now vast list of software solutions. Just like SKM, ETAP has the Network Analysis solution that includes arc flash analysis, load flow analysis, short-circuit analysis, and so on.

Today’s version of software packages gives engineers the option of drawing the whole electrical system as a one-line diagram. The software requires engineers to input information for each component to allow the program to perform its calculation. When the input information is completely placed in the one-line, the program conducts all calculations selected from the list mentioned before at once. It will even give the user warnings and errors when information is missing or abnormalities appear in the results. Compared with the old way of using Excel spreadsheets, software packages are convenient and save engineers time when a change in design occurs. Engineers simply need to open one file, make the changes in that file, and all of the calculations will be updated simultaneously.

Documentation is also as convenient as performing calculations when using these software packages. Results can be shown in the one-line, but the software can create reports where it shows all parameters and results in a single document. This is great for quality control, including the documentation of all of calculations. Also, files can be imported into AutoCAD. As a result, creating panelboard schedules using software packages is one of the more valuable tools that an electrical engineer can use.

Using software packages might be overkill for some projects. That is why it is important to understand the project’s electrical scope before deciding what tool to use. Sometimes the project is small enough that using Excel templates alone will accomplish the calculations needed. If an engineer or company already has access to software packages like SKM or ETAP, the following rules of thumb can be applied to help you decide whether to use them:

Determine if the project includes any of the following tasks:

Performing voltage drop calculations for more than three feeders

Performing short circuit calculations for a multi-voltage level system

Creating five or more panelboard calculations.

If these items apply to the project, then a sophisticated software package like SKM is a good candidate for performing calculations. Setting up the project accordingly from the beginning will be beneficial for both the project and the engineer’s work.

Additional tools

Another general tool available to electrical engineers is the Internet. However, be cautious to avoid relying on untrustworthy Web sources. The most trusted sites for electrical information typically are the manufacturers’ websites. With their help, electrical engineers can get information values that can help select equipment. Some manufacturers might even perform calculations for the engineer, saving time and resources. Developing a strong relationship with manufacturers and their representatives is key for electrical engineers.

There are also online discussion forums available to assist engineers in decision-making. Mike Holt's Forum is a great place where new and seasoned engineers exchange knowledge for the same purpose: to achieve the best design possible. Engineers can talk to industry peers to help guide them in the completion of their design. Magazine articles are an additional tool to keep current with today’s technology.

Future

Even though engineers started using AutoCAD as a tool for creating technical drawings, computer-aided drafting software products are moving toward performing calculations that can be used in combination with the drawings. These types of software products are marketed as CAD because of their additional capability of mathematical modeling. As explained before, by having calculations, drawings, and reports under one roof, electrical engineers can minimize labor hours and human error, specifically when making changes to the design. Software products like Autodesk MEP and Revit are incorporating plans with families, elements, schedules, and diagrams, making the electrical power system analysis and design more integrated than ever before.

With time, electrical engineers will develop their own best practices and will bring new skills to the table, leaving their own footprint on the project design. It is important to keep in mind that just because machines can provide quicker and clearer results, they may not always be the best option. Understanding the true benefits of any tool is essential for engineers to efficiently design and review results, specifically to aid in supporting and documenting their design decisions in the event other engineers, clients, or reviewers inquire about the electrical system.

Manuel E. Hernandez is an electrical engineer with Primera Engineers. He has experience in building systems engineering for a variety of projects in the commercial, educational, and health care markets; his experience includes the use of SKM Power Tools software, Arc Flash Analysis, and AutoCAD drafting.

Thank you Mr. Hernandez for your interesting article.
The softwares you have mentioned in the article are mainly used in power engineering. However, when you deal with Residential and Commercial occupancies, where the NEC must be applicable, those softwares are not useful since they don't take into consideration the multiple requirements of the Code. On the other hand, the available spreadsheets are not designed for commecial use (mostly, particular use), the application of the NEC is in many cases superficial, poor interfase, prone to errors when data has to be editted, limited to two or three tiers of feeders, etc.
My question is: Do you know a pro software package oriented to the application of the NEC whose purpose is the calculation of service/branch-ckts/feeders, taking into consideration demand loads, wire/conduit/busway sizes, OCP, different load types and occupancies, step-down transformers, etc., including a recap report of the input data and a report of the corresponding results?. Your assistance will be appreciated.
Thank you,
Jacobo Mendelovici
j.mendelov@gmail.com

ANANTHA , Non-US/Not Applicable, India, 12/12/13 01:54 AM:

Interesting. Glad if a hard copy is got

Anonymous , 08/17/14 01:04 PM:

At Beginnig when I have been working at EBASCO Services Inc. 1990 it was no spreadsheet Excel. I bought Lotus 1-2-3 and QBasic and because it were a lot of calculations I made myself software cor current calculations and drop voltage and short circuit calc. Latter MS proposed me in leu of concurence to change my Lotus to Excel 4 for free and I decided to make. After I reused my software programs on Excel 4 and it was great in the moment we used AutoCAD 10 and 11 (DOS) later we got 12 version still DOS?Windows 3.0/3.1 And all was speedy more. Good time the SKM came and latter ETAP it was to expensive for me to buy. Ami Joseph